Longitudinal Wave Locally Resonant Band Gaps in Metamaterial-Based Elastic Rods Comprising Multi-Degree-of-Freedom DAVI Resonators

The wave propagation and vibration transmission in metamaterial-based elastic rods with periodically attached multi-degree-of-freedom (MDOF) dynamic anti-resonant vibration isolator (DAVI) resonators are investigated. A methodology based on a combination of the transfer matrix (TM) method and the Bloch theorem is developed, yielding an explicit formulation for the complex band structure calculation. The bandgap behavior of the periodic structure arrayed with single-degree-of-freedom (SDOF) DAVI resonators and two-degree-of-freedom (2DOF) DAVI resonators are investigated, respectively. A comparative study indicates that the structure consisting of SDOF DAVI resonators periodically jointed on the metamaterial-based elastic rod can obtain an initial locally resonant band gap 500 Hz smaller than the one given in the published literature. The periodic structure containing 2DOF DAVI resonators has an advantage over the periodic structure with SDOF DAVI resonators in achieving two resonance band gaps. By analyzing the equivalent dynamic mass of a DAVI resonator, the underlying mechanism of achieving a lower initial locally resonant band gap by this periodic structure is revealed. The parameters of the 2DOF DAVI resonator are optimized to obtain the lowest band gap of the periodic structure. The numerical results show that, with the optimal 2DOF DAVI parameters, the periodic structure can generate a much lower initial locally resonant band gap compared with the case before the optimization

Longitudinal Wave Locally Resonant Band Gaps in Metamaterial-Based Elastic Rods Comprising Multi-Degree-of-Freedom DAVI Resonators

The wave propagation and vibration transmission in metamaterial-based elastic rods with periodically attached multi-degree-of-freedom (MDOF) dynamic anti-resonant vibration isolator (DAVI) resonators are investigated. A methodology based on a combination of the transfer matrix (TM) method and the Bloch theorem is developed, yielding an explicit formulation for the complex band structure calculation. The bandgap behavior of the periodic structure arrayed with single-degree-of-freedom (SDOF) DAVI resonators and two-degree-of-freedom (2DOF) DAVI resonators are investigated, respectively. A comparative study indicates that the structure consisting of SDOF DAVI resonators periodically jointed on the metamaterial-based elastic rod can obtain an initial locally resonant band gap 500 Hz smaller than the one given in the published literature. The periodic structure containing 2DOF DAVI resonators has an advantage over the periodic structure with SDOF DAVI resonators in achieving two resonance band gaps. By analyzing the equivalent dynamic mass of a DAVI resonator, the underlying mechanism of achieving a lower initial locally resonant band gap by this periodic structure is revealed. The parameters of the 2DOF DAVI resonator are optimized to obtain the lowest band gap of the periodic structure. The numerical results show that, with the optimal 2DOF DAVI parameters, the periodic structure can generate a much lower initial locally resonant band gap compared with the case before the optimization

Spatiotemporal high-resolution mapping of biological production in the Southern Ocean

Abstract The Southern Ocean is considered to play an important role in the global biogeochemical cycles of carbon and nutrients. It is still unclear how biological production there impacts climate change owing to the remarkable gap between the current and the ideal state of research. Here, we proposed a new concept of combining Neural Network based parameterization of dissolved inorganic carbon with Biogeochemical Argo floats, showing simultaneously spatiotemporal distributions of net community production and resupply of carbon from the deep ocean based on the dissolved inorganic carbon change. It indicated a total net community production of 4.1 ± 0.3 Pg-C year−1 over the Southern Ocean, which accounts for 45% of global annual oceanic carbon export and is 20% higher than the previous estimates. Furthermore, net community production in the Southern Ocean has decreased by 0.8% year−1 since the 2010s, indicating that it may be contributing as positive feedback to global warming

Energy‐efficient train timetabling for a medium‐speed maglev line considering propulsion and suspension energy consumption

Abstract This paper addresses the energy‐efficient train timetabling problem for MSM systems, where both propulsion and suspension energy consumption are considered. The timetable design problem is modelled as a bi‐level model for a complete two‐way MSM line. The upper level determines the train departure time at the first station, which makes train operations more convenient for passengers. The lower level uses an empirical description of the train energy consumption as a function of segment running times, and an energy‐efficient timetable optimization model is built. In doing so, all the services in both directions along a certain planning horizon are considered while attending to a known passengers’ demand. Moreover, the convenience of considering energy consumption as part of a broad objective function that includes other relevant costs is pointed out. Then, a unified sequential solution algorithm is developed for an efficient and accurate solution of the bi‐level model. Experiments show that the proposed framework can generate a holographic timetable of energy‐efficient MSM containing multi‐dimensional variables such as time, space, velocity, and electrical quantities

The impact of social capital on rural residents ' income and its mechanism analysis —Based on the intermediary effect test of non-agricultural employment

Agricultural, rural, and farmer-related issues are of pivotal importance, significantly influencing the evolution of our party, nation, and state. Central to these multifaceted issues, the farmer's plight is three-fold: low earnings, the hardship of income augmentation, and a pronounced socioeconomic divide between rural and urban areas. The crux of resolving these agricultural, rural, and farmer-related issues lies in elevating the income levels of farmers. Utilizing data from the China Family Panel Studies (CFPS) 2018, this study probes the influence of social capital on the earnings of rural dwellers and delves into the intermediary role of non-agricultural employment. The findings indicate a substantial and positive correlation between social capital and rural income. The conclusions remain robust even after applying instrumental variable methods to counteract endogeneity. Mediation analysis reveals that social capital significantly boosts opportunities for non-agricultural employment, which, in turn, enhances the income of rural residents. Therefore, the roles of social capital and non-agricultural employment in income augmentation warrant careful consideration